Caller ID is a telephone on-hook capability that provides a called party with information about the caller before the incoming call is answered. Conventionally, such information includes the date and time of the call and the caller's telephone number. A data message, preceded by a channel seizure signal, is sent in conjunction with the ringing signal from the central office to the called party during the silent interval after the first 20-Hz, 2-second ringing phase.
Caller ID service is designed for use with the voice portion of existing loop connections. The digitally formatted message is transmitted through a stream of data bits of standardized digital format. The message is sent once, without retransmission capability. The channel seizure signal, sent at the beginning of each message to alert the called party equipment of the coming information through physical connection of an appropriate interface, is typically composed of thirty continuous bytes of octal 125 (i.e., 01010101), or 250 milliseconds of a 600-Hz square wave. Transmission of data follows thereafter and is completed prior to the next 20-Hz ringing signal. For a detailed description of the method and apparatus for sending the data message, reference is made to U.S. Pat. No. 4,551,581 issued to Doughy on Nov. 5, 1985.
The receiving display apparatus at a caller ID subscriber location may be as disclosed in U.S. Pat. No. 4,582,956, issued Apr. 15, 1986. The apparatus, which may be a part of a telephone instrument or a stand-alone device, includes a line interface unit, a converter, a control circuit and a display unit. A frequency shift keyed (ASK) signal representing the special service information is filtered from the ringing signals by the line interface unit. The converter detects the ASK signal and demodulates the special service information from the ASK signal. Following detection of the ASK signal, the control circuit receives and stores the special service information. The stored information is periodically sent to the display unit to begin exhibiting thereof during the silent interval before the next ringing signal.
A problem in identifying a caller in a commercial environment, such as a fleet of vehicles having mobile telephones, is recognized in U.S. Pat. No. 5,274,699, issued to Ran on Dec. 29, 1993. As different drivers often operate vehicles at different times, transmission of a vehicle ID to a dispatcher, for example, would identify the vehicle but not the user. To overcome this problem, each mobile communication unit includes a keyboard and enhanced display to enable the caller to substitute an "alias ID" for the vehicle phone ID. Before placing a call, the user can display all stored alias ID information, select or edit an alias ID or choose not to transmit an alias ID, and then initiate communication through wireless transmission with another mobile communication unit or dispatcher.
The caller ID service in the public switched telephone network (PST) offers several advantages to the called party subscriber. Identification of the calling party, as provided by the caller ID service, allows the called party to screen an incoming call personally before its completion and thereby to decide whether or not it is desirable to answer the call. Nuisance calls, such as advertising and solicitation calls, can be avoided if the identity of the caller is determined beforehand. Knowledge of caller identity also serves as a resource for dealing with and curtailing harassment calls.
Reference is made to U.S. Pat. No. 5,497,414, issued to Bartholomew on Mar. 5, 1996, for a discussion of the advantages to the called party subscriber as well as the countersinking disadvantageous effects on the caller's privacy. If the caller number identity is made known to a called party caller ID subscriber each time a call is made, the privacy afforded to a caller having an unlisted number is significantly compromised. Similarly, any caller may find it desirable to place a call without revealing origination identity to the called party. In such case, the caller must take the risk that the called party line does not subscribe to the caller ID service.
As a recourse, the caller in some existing systems is given the option to block transmission of caller line origination identity to the called party. If the called party is a caller ID service subscriber, the display unit will either indicate a caller privacy condition or remain blank. Reference is made to U.S. Pat. No. 5,161,181, issued to Zwick on Nov. 3, 1992, for discussion of this concept. With caller ID blocked, a call is directed to the called party for completion in the standard manner and the functionality of caller ID is lost, along with its advantages to the called party subscriber. The caller can thus retain anonymity with an increased likelihood that the called party will elect not to answer the call.
Accommodating the requirements of called party subscribers to screen the origination of incoming calls before answering, while permitting calling subscribers to individually control what origination information will be transmitted for placed calls, is an ongoing concern of service providers. Enhancements to the basic caller ID service have further complicated these considerations.
With one such enhancement the network provides the caller's name as well as the caller's number for display at the caller ID box of the called party. The phrase "enhanced service" as used hereinafter refers to the capability of supplying both text and telephone caller identification information. A caller who blocks caller ID to avoid a return call from the called party may find benefit in transmitting the name information alone for identification purposes. Conventionally, the ability to transmit name information without originating telephone number information is not available. Moreover, the provision of additional caller ID information increases the risk that misleading information will be transmitted. For example, a call may be placed from a subscriber location at which several people reside. If the caller is not the listed subscriber, the called party may not recognize the identified caller name and choose not to answer the call. Identification of the name of the actual caller instead of the name of the subscriber is a function that prior art telephone systems lack. Such a function would be a benefit both to the called party, who may know the called party and thus answer the call, and the calling party who is more likely to have the call completed.
Complications also arise with callers that subscribe to distinctive ringing type services that provide a plurality of telephone numbers for the same subscriber line. The distinctive ringing service subscriber may reserve one number for important calls, which would be answered under most circumstances, while using another number for less important calls that the subscriber may choose to ignore. Alternatively, each number may be associated with a different resident, the intended called party being indicated by the distinctive ring. In other circumstances a subscriber may require two telephone numbers for a single line to distinguish between business calls and personal calls. The business name would be listed for the business number, while the subscriber's name would be listed for the personal use number.
Conventionally, one of the listings for the multiple number line is recognized as a primary listing, the remainder as secondary listing(s). A called party subscriber to the basic caller ID service would receive from a multiple line calling subscriber a display of the caller's primary telephone number. A called party subscriber to the enhanced caller ID service would additionally have displayed the primary name associated with the primary number. The calling party may not wish to transmit the primary number and its associated listed name for a particular call. Depending upon the purpose of the call, a secondary number listing may be appropriate. A similar situation exists with a business subscriber who has a plurality of stations, each with a direct dial number. A caller from one of the stations may wish to select among several numbers to be displayed to the called party. The need thus exists for distinguishing between numbers, as well as names, for an individual call.